Composite pipe construction



April 93 J. A. STADTFELD 2,076,210

COMPOS ITE PIPE CONSTRUCTION Filed July 6, 1936 INVENTOR. [4005 A. Snarrao.

ATTORNEY Patented Apr. 6, 1937 UNITED STATES.

PATENT OFFICE COMPOSITE rm: cons'rauc'non Jacob A. Stadtfeld, San Francisco, Calii'., assignor to Williams-Wallace Company, a corporation oi! California;

Application July c, 1926, Serial No. 88,936

1 Claims. (cl. 138-63) longitudinally with respect to the outer shell and means cooperating with said pipes for permitting while at the same time limiting the extent of said m longitudinal movement.

Another object of my invention is to provide a positive interlock between said members. 1

Another object of my invention is to provide means between spaced walls of a two wall pipe 15 structure in combination with a strip or ring type spacing means to holdzsaid spacing means in correct longitudinal position. Y

Another object of my invention is to provide a form of spacing means betwen twin-walled 20 piping having the minimum number of contacts with said walls'which is geometrically possible. Another object of my invention is to provide a novel form of spacing means composed of a,

substantially rigid polygonal ring member adapt- 25 ed to bear on its points against the outer tube and to contact the inner tube on its straight sides substantially intermediate the points.

Another object of my invention is to provide a novel form of rigid spacing member made up 30 in laminated form, impregnated with cement and kiln dried. k T v Other objects and advantages of my invention will be apparent from the following description in which like reference numerals have been used on corresponding parts in all the figures, and in which: L a k Fig. 1 is a view in perspective with the walls ipartly broken away to show the interior construcon; 7 40 Fig. 2 s a cross-section view taken on the line 2-2 of Fig. 1;

Fig. 3 is a view in perspective of the spacing means; V

Fig. 4 is a view in perspective'of another form 45 of my invention; and r Fig. 5 is a cross-section view taken on the line 5-5 of Fig. 4.

This invention is an improvement on my prior Patent No. 2,013,193. My invention provides a solution for the problem of positively locking the inner slidable tube within the outer tube and thereby making it impossible for the pipe to be installed in use with 55 the inner tube removed, as it'is possible to do with my earlier types The present invention therefore produces a composite pipe which is safer and more acceptable to the flre underwriters and mak 9 men to slip outthe inner pipe. It also obviates it impossible for dishonest workthe risk that in sh pping and handling the inner tube will become dislodged and lost.

I shall now describe the construction of one section or unit of the pipe. of these units are joined together to make the In use, a plurality completed pipe. Each unit may be of any desired length. a

The outer tube or shell in may be formed up from a flat sheet and joined by means of lap joint H. One end is crimped at I 2 to form the male member of the joint and to give a reduced diameter to this end of the tube. Near its opp-.v

site end an internal annular ridge i3 is formed which may or may not extend all the way around the shell depending upon the designers choice.

The inner tube or shell I is likewise formed up from a flat sheet and joined by means of a lap joint l6. One end is crimped at IT to form the male portion of a joint. External annular ridges l8 and I9 or their equivalent are. formed on the outer wall of shell l5. These are located in from the ends of the inner shell 9. distance which is determined in relation to the annular ridge 43 in the outer shell and the crimped end l2, respectively. 5 distance is determined by the length of the spacing member 2|] plus the amount.

of longitudinal movement it is desired that the inner tube should have with relation to the outer tube,--usually three or four inches in each direction from a central position.

It is notnecessary that the crimped end of the outer tube should have an external annular ridge l3, although it may be provided if desired, since the inwardly tapered end 12, being of reduced diameter, has the effect of holding the spacing member 20 within it.

The spacing member ill, (see Fig. 3) is shown in the form of a pentagon since that is the particular geometrical form adapted to flt the particular annular space iormed between tube Ill and tube IS. The space between tube Ill and tube 15 for the most sizes of pipe is inch, therefore the larger the diameter of the pipe, thegreater the number of sides necessary on the spacing member 20 for it to fit the space. It is one of the purposes of my invention to support and space the inner and outer tubes with relation to each otherby members 20 having as few points of physical contact extending between the walls of each tube as is geometrically possible. This minimizes the heat conduction from one to the other and also allows a maximum air cell between the -tubes.

I have found it preferable to make the spacer M of a laminated a material,-usually aboutflve layers wrapped from a continuous strip. when wrapped it is impregnated with a cement and then kiln dried. This causes it to become very hard and rigid in form, hence well adapted or my purpose. The sides 2| of the member 20 are substantially straight and the corners 22 have a slight curvature. The longitudinal length of each member 20 is to be determined by the weight and size of the tubes In and I5, having in minrhthe strain of the load to be put on it. In the usual sizes, suitable for most household installations, I have found that an inch and a half to two inches is a suitable length. However, it may be longer or shorter according to the particular designers choice, but in order to allow for the longitudinal sliding of the inner tube III, the length should be less, for instance, than the distance between the internal annular flange IS on the outer tube, and the external annular flange I8 on the. inner tube.

The relative sliding of the inner tube within the outer is not only a convenience when joining is heated greatly exceeds that of the outer tube and therefore the former is subject to greater expansion and contraction than the latter. This is further accentuated by the fact that the present practice is to use aluminum .for the inner pipe and galvanized sheet iron for the outer pipe.

In the modification shown in Figs. 4 and 5 the same principles apply as already explained, the only difference being that with the rectangular pipe the shape of the spacing member differs and the means on the inner tube, projecting into the annular spacing, instead of being a ridge like l8 and is of Fig. 1, is usually a piece of metal 30 welded to the inner tube and projecting over its ends 3| where it engages the sides 32 of .spacing member 33. It may, however, be obtained in other ways and still be within the scope of my invention.

The ridge on the outer pipe corresponding with of Fig.- 1 may be formed by a swage as at 35, where it is adapted tobeengaged by theside 36 of the spacing member. The location of the projections 3| and 35 is governed by the same conditions as was explained in connection with Fig. 1 and opposite ends are similarly crimped (not =-shown) topermit a. plurality of the units to be joined together to form a long pipe.

The manner of assembling a unit of pipe is as follows: I

Spacing members '20 are slipped on eachend of a section of inner tube IS with external annular ridges l8 and I9. Thissub-assembly is then slipped inside the outer tube ill from the uncrimped end. It will not slide out the other end because of the reduced diameter due to the crimping l2. The sub-assembly is then locked inside the outer tube I! by forming the internal ridge l8.

While I have shown one formof my invention,-

I therefore claim my invention as follows: ,1. A spacing member adapted for insertion between a pair of spaced walls, comprising a. polyg onal' member formed from a plurality of layers of thin asbestos strips impregnated with a cement to form the same into a rigid one-piece whole.

2. In a composite pipe construction the combination of an outer shell, an inner shell spaced therefrom, both of saidshells having spaced annular ridges formed thereon and projecting into the annular space between said. pipes, and spacing means in said annular space adapted to hold said inner and outer shells in spaced annular relation to each other and to cooperate with said annular ridges to limit the relative longitudinal shifting of said inner shell within said outer shell.

3. In a composite pipe construction the com: bination of an outer shell having one end, tapered inwardly, thereby restricting the opening therein'and an internal annular ridge near the opposite end, an inner shell of smaller diameter than the aforementioned shell, having external annular ridges formed therein away from its ends, and spacing means inserted in the annular space between said pipes to hold them in spaced annular relation to each other and also to limit the longitudinal movement of the inner pipe by means of said annular ridges abutting the edges of said spacing means.

4. In a composite pipe construction of the type having an inner and an outer shell arranged in spaced relation to each other, the combination of a continuous polygonal spacing means having substantially straight sides and contacting the walls of said pipes at the fewest number of points which is geometricallypossible.

5. In a composite pipe construction the combination of an outer shell, an inner shell spaced therefrom, both of said shells having means thereon which project into the annular space between said pipes, and spacing means in said annular space adapted'to hold said inner and outer shells in spaced annular relation to each.

with said annular ridges to limit the relative longitudinal shifting of said inner shell within said outer shell.

7. In a composite pipe construction the combination of an outer, shell having one end tapered inwardly, thereby restricting the opening therein and an internal annular ridge near the opposite end, an inner shell of smaller diameter than the aforementioned shell, having external annular ridges formed therein away from its ends, and a pair of spacing means inserted in the annular space between said pipes to hold them in spaced annular relation to each other and also to limit the longitudinal movement of the inner pipe by means of said annular ridges abutting the edges of said spacing means.

1 JACOB A. STADTFELD. 

